/// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
///
/// Developed at SunPro, a Sun Microsystems, Inc. business.
/// Permission to use, copy, modify, and distribute this
/// software is freely granted, provided that this notice
/// is preserved.

#include "../detail/type_float.hpp"
#include "../ext/scalar_constants.hpp"
#include <cmath>
#include <cfloat>

#if(GLM_COMPILER & GLM_COMPILER_VC)
#	pragma warning(push)
#	pragma warning(disable : 4127)
#endif

typedef union {
    float value;
    /* FIXME: Assumes 32 bit int.  */
    unsigned int word;
} ieee_float_shape_type;

typedef union {
    double value;
    struct {
        int lsw;
        int msw;
    } parts;
} ieee_double_shape_type;

#define GLM_EXTRACT_WORDS(ix0, ix1, d)        \
    do {                                    \
        ieee_double_shape_type ew_u;        \
        ew_u.value = (d);                    \
        (ix0) = ew_u.parts.msw;                \
        (ix1) = ew_u.parts.lsw;                \
    } while (0)

#define GLM_GET_FLOAT_WORD(i, d)                \
    do {                                    \
        ieee_float_shape_type gf_u;            \
        gf_u.value = (d);                    \
        (i) = gf_u.word;                    \
    } while (0)

#define GLM_SET_FLOAT_WORD(d, i)                \
    do {                                    \
        ieee_float_shape_type sf_u;            \
        sf_u.word = (i);                    \
        (d) = sf_u.value;                    \
    } while (0)

#define GLM_INSERT_WORDS(d, ix0, ix1)            \
    do {                                    \
        ieee_double_shape_type iw_u;        \
        iw_u.parts.msw = (ix0);                \
        iw_u.parts.lsw = (ix1);                \
        (d) = iw_u.value;                    \
    } while (0)

namespace glm {
    namespace detail {
        GLM_FUNC_QUALIFIER float nextafterf(float x, float y) {
            volatile float t;
            int hx, hy, ix, iy;

            GLM_GET_FLOAT_WORD(hx, x);
            GLM_GET_FLOAT_WORD(hy, y);
            ix = hx & 0x7fffffff;        // |x|
            iy = hy & 0x7fffffff;        // |y|

            if ((ix > 0x7f800000) ||    // x is nan
                (iy > 0x7f800000)) {    // y is nan
                return x + y;
            }
            if (abs(y - x) <= epsilon<float>()) {
                return y;
            }        // x=y, return y
            if (ix == 0) {                // x == 0
                GLM_SET_FLOAT_WORD(x, (hy & 0x80000000) | 1);// return +-minsubnormal
                t = x * x;
                if (abs(t - x) <= epsilon<float>())
                    return t;
                else
                    return x;    // raise underflow flag
            }
            if (hx >= 0) {                        // x > 0
                if (hx > hy)            // x > y, x -= ulp
                    hx -= 1;
                else                // x < y, x += ulp
                    hx += 1;
            }
            else {                        // x < 0
                if (hy >= 0 || hx > hy)    // x < y, x -= ulp
                    hx -= 1;
                else                // x > y, x += ulp
                    hx += 1;
            }
            hy = hx & 0x7f800000;
            if (hy >= 0x7f800000)
                return x + x;        // overflow
            if (hy < 0x00800000)        // underflow
            {
                t = x * x;
                if (abs(t - x) > epsilon<float>()) {                    // raise underflow flag
                    GLM_SET_FLOAT_WORD(y, hx);
                    return y;
                }
            }
            GLM_SET_FLOAT_WORD(x, hx);
            return x;
        }

        GLM_FUNC_QUALIFIER double nextafter(double x, double y) {
            volatile double t;
            int hx, hy, ix, iy;
            unsigned int lx, ly;

            GLM_EXTRACT_WORDS(hx, lx, x);
            GLM_EXTRACT_WORDS(hy, ly, y);
            ix = hx & 0x7fffffff;                                // |x|
            iy = hy & 0x7fffffff;                                // |y|

            if (((ix >= 0x7ff00000) && ((ix - 0x7ff00000) | lx) != 0) ||    // x is nan
                ((iy >= 0x7ff00000) && ((iy - 0x7ff00000) | ly) != 0)) {    // y is nan
                return x + y;
            }
            if (abs(y - x) <= epsilon<double>()) {
                return y;
            }                                    // x=y, return y
            if ((ix | lx) == 0) {                                                    // x == 0
                GLM_INSERT_WORDS(x, hy & 0x80000000, 1);        // return +-minsubnormal
                t = x * x;
                if (abs(t - x) <= epsilon<double>())
                    return t;
                else
                    return x;   // raise underflow flag
            }
            if (hx >= 0) {                             // x > 0
                if (hx > hy || ((hx == hy) && (lx > ly))) {    // x > y, x -= ulp
                    if (lx == 0)
                        hx -= 1;
                    lx -= 1;
                }
                else {                            // x < y, x += ulp
                    lx += 1;
                    if (lx == 0)
                        hx += 1;
                }
            }
            else {                                // x < 0
                if (hy >= 0 || hx > hy || ((hx == hy) && (lx > ly))) {// x < y, x -= ulp
                    if (lx == 0)
                        hx -= 1;
                    lx -= 1;
                }
                else {                            // x > y, x += ulp
                    lx += 1;
                    if (lx == 0)
                        hx += 1;
                }
            }
            hy = hx & 0x7ff00000;
            if (hy >= 0x7ff00000)
                return x + x;            // overflow
            if (hy < 0x00100000) {                        // underflow
                t = x * x;
                if (abs(t - x) > epsilon<double>()) {                    // raise underflow flag
                    GLM_INSERT_WORDS(y, hx, lx);
                    return y;
                }
            }
            GLM_INSERT_WORDS(x, hx, lx);
            return x;
        }
    }//namespace detail
}//namespace glm

#if(GLM_COMPILER & GLM_COMPILER_VC)
#	pragma warning(pop)
#endif

namespace glm {
    template<>
        GLM_FUNC_QUALIFIER float nextFloat(float x) {
            #		if GLM_HAS_CXX11_STL
            return std::nextafter(x, std::numeric_limits<float>::max());
            #		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
            return detail::nextafterf(x, FLT_MAX);
            #		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
            return __builtin_nextafterf(x, FLT_MAX);
            #		else
            return nextafterf(x, FLT_MAX);
            #		endif
        }

    template<>
        GLM_FUNC_QUALIFIER double nextFloat(double x) {
            #		if GLM_HAS_CXX11_STL
            return std::nextafter(x, std::numeric_limits<double>::max());
            #		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
            return detail::nextafter(x, std::numeric_limits<double>::max());
            #		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
            return __builtin_nextafter(x, DBL_MAX);
            #		else
            return nextafter(x, DBL_MAX);
            #		endif
        }

    template<typename T>
        GLM_FUNC_QUALIFIER T nextFloat(T x, int ULPs) {
            GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'next_float' only accept floating-point input");
            assert(ULPs >= 0);

            T temp = x;
            for (int i = 0; i < ULPs; ++i) {
                temp = nextFloat(temp);
            }
            return temp;
        }

    GLM_FUNC_QUALIFIER float prevFloat(float x) {
        #		if GLM_HAS_CXX11_STL
        return std::nextafter(x, std::numeric_limits<float>::min());
        #		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
        return detail::nextafterf(x, FLT_MIN);
        #		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
        return __builtin_nextafterf(x, FLT_MIN);
        #		else
        return nextafterf(x, FLT_MIN);
        #		endif
    }

    GLM_FUNC_QUALIFIER double prevFloat(double x) {
        #		if GLM_HAS_CXX11_STL
        return std::nextafter(x, std::numeric_limits<double>::min());
        #		elif((GLM_COMPILER & GLM_COMPILER_VC) || ((GLM_COMPILER & GLM_COMPILER_INTEL) && (GLM_PLATFORM & GLM_PLATFORM_WINDOWS)))
        return _nextafter(x, DBL_MIN);
        #		elif(GLM_PLATFORM & GLM_PLATFORM_ANDROID)
        return __builtin_nextafter(x, DBL_MIN);
        #		else
        return nextafter(x, DBL_MIN);
        #		endif
    }

    template<typename T>
        GLM_FUNC_QUALIFIER T prevFloat(T x, int ULPs) {
            GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'prev_float' only accept floating-point input");
            assert(ULPs >= 0);

            T temp = x;
            for (int i = 0; i < ULPs; ++i) {
                temp = prevFloat(temp);
            }
            return temp;
        }

    GLM_FUNC_QUALIFIER int floatDistance(float x, float y) {
        detail::float_t<float> const a(x);
        detail::float_t<float> const b(y);

        return abs(a.i - b.i);
    }

    GLM_FUNC_QUALIFIER int64 floatDistance(double x, double y) {
        detail::float_t<double> const a(x);
        detail::float_t<double> const b(y);

        return abs(a.i - b.i);
    }
}//namespace glm
